Profiles of plasma progesterone in ovariectomized beef
cows revealed that once-used CIDR devices maintained
concentrations greater than or equal to 1.0 ng/mL, whereas twice-used devices resulted in a mean concentration of progesterone of 0.9 ng/mL [18] suggesting the possibility of reduced fertility from the use of a twice-used CIDR. These
findings are in disagreement with the results obtained from
the current experiment. Although the mean concentration
of progesterone between animals receiving a once-used
versus twice-used CIDR device (Fig. 1) was significantly
different (3.37 Æ 0.5 and 1.40 Æ 0.5 ng/mL, respectively; P ¼ 0.01), the concentration of plasma progesterone on the
day of device removal in an animal receiving a twice-used
CIDR was greater than 1 ng/mL, indicating a sufficient